Search PubMed⌕ Search

Biomedical subjects

P Lewis

Publications and source records attributed to P Lewis.

At least 199 records · Page 11Linked to original sources
PubMed1979

Cyclosporin A initially as the only immunosuppressant in 34 recipients of cadaveric organs: 32 kidneys, 2 pancreases, and 2 livers.

34 patients treated with cyclosporin A received 36 cadaveric organ allografts (32 kidneys, 2 pancreases, and 2 livers), 26 kidneys are still supporting life, 3 after more than a year; the pancreases and livers are also functioning. 20 patients are not receiving steroids, and 15 of these have not had any additional immunosuppressive agents. In these patients infectious complications have not been severe, but a gastroduodenal lymphoma has developed in 1 patient. 6 patients were given 'Cytimum' (a cyclophosphamide derivative) and steroids in addition to cyclosporin A: 5 of these died of infections and 1 also had a lymphoma. 11 patients received additional steroids: 1 of these died from septicaemia and lymphoma. Nephrotoxicity can be avoided by perioperative hydration and forced diuresis. Cyclosporin A is effective on its own and is a very potent immunosuppressive drug. Additional immunosuppressive agents may lead to severe complications.

Adult↗
PubMed1979

Fetal breathing: a review.

The history, physiology, pharmacology, and clinical application of fetal breathing are reviewed. Early optimism that measurements of fetal breathing would aid in perinatal management decisions has remained unfulfilled. Problems to be overcome include standardization of technique and measurement parameters and allowance for physiologic variations. Recent research developments indicate that the likely role of fetal breathing in perinatal medicine will be in conjunction with other established tests of fetal health.

Amniocentesis↗
PubMed1979

Prospective study of genetic counselling.

A prospective study was carried out on 200 consecutive subjects seen for counselling (consultands) for serious genetic disorders. Educational and social background of consultands and their knowledge and understanding of their particular problem were assessed before counselling, and their response was determined immediately afterwards and three months and two years later by an independent observer not concerned in the genetic counselling. The husband's educational background was particularly important in influencing a couple's comprehension of counselling. X-linked recessive and chromosomal disorders presented the most difficulties in comprehension. The counsellors' assessment of comprehension was a good guide to the consultands' comprehension as assessed at subsequent follow-up. The proportion deterred from having children increased with time and over a third had been sterilised within two years of counselling. It is suggested that follow-up after counselling should be routine, especially when the counsellor suspects that comprehension has not been good, in X-linked recessive and chromosomal disorders, and when the risks of having an affected child are considered to be high.

Adult↗
PubMed1979

Signal-controlled responding.

Pigeons' key pecks were reinforced with grain, then extinguished. An 8-second tone preceded the availability of peck-dependent grain 1 second after tone offset. When a tone signalled grain and an 8-second clicking sound did not, three pigeons pecked during a high percentage of tone periods, but they pecked during a low percentage of click periods. When the roles of the tone and clicking sound were reversed, performance reversed. For other birds, when a key peck during the tone cancelled the availability of grain (omission procedure), the tendency to key peck during the tone decreased some, but still remained high. A third group of pigeons received the omission procedure with the addition that the tone could not end unless 2 seconds had elapsed without a key peck. The pigeons continued to respond in a high percentage of tone periods. The experiments favor an explanation based on the pairing of the tone with a reinforced response, such as Pavlovian conditioning.

Journal Article↗
PubMed1979

Effects of response-independent negative reinforcers on negatively reinforced key pecking.

Previous research has shown that presenting response-independent positive reinforcers reduces the response rate of an operant maintained by positive reinforcement. The present experiment investigated a similar effect using shock-free time as a negative reinforcer. Brief shocks were delivered in the presence of a distinctive stimulus, and pigeon's key pecks were reinforced by the occasional presentation of a 2-minute shock-free period. Extra 2-minute shock-free periods were added independently of behavior. For each of three pigeons, response rate during shock-on periods declined with added shock-free periods; the more frequently the extra shock-free periods occurred the greater the decline in response rate. This outcome is predicted by extending the Law of Effect to include negative reinforcement.

Journal Article↗
PubMed1978

Effects of subliminal and supraliminal stress on symptoms of anxiety.

Two experiments were carried out with volunteer subjects to test whether the subliminal viewing of emotive material induced anxiety and its associated bodily symptoms. In one experiment 24 subjects looked at anxiety-inducing words presented singly through a tachistoscope under supraliminal or subliminal conditions, and in the other study 50 subjects looked at a neutral and an emotive movie film under similar conditions. Subliminality was insured in the first experiment by reducing the duration of exposure and in the second by reducing the level of illumination. The results showed that ratings of anxiety were significantly increased under subliminal emotive conditions, and reduced following subliminal neutral exposure. Correlations between psychic and somatic symptoms of anxiety were significantly higher under supraliminal conditions compared with subliminal ones. The possible role of subliminal stimulation in investigating the psychic and somatic components of anxiety is discussed.

Adolescent↗
PubMed1978

Purification of virus-specific RNA from chicken cells infected with avian sarcoma virus: identification of genome-length and subgenome-leghth viral RNAs.

Avian sarcoma virus (ASV)-specific RNA was purified from ASV-infected cells by using hybridization techniques which employ polydeoxycytidylic acid-elongated DNA complementary to ASV RNA as well as chromatography on polyinosinic acid-Sephadex columns. The purity and nucleotide sequence composition of purified, virus-specific RNA were established by rehybridization experiments and analysis of labeled RNase T1-resistant oligonucleotides by two-dimensional polyacrylamide gel electrophoresis. Polyadenylic acid-containing RNA purified from ASV-infected cells contained approximately 1 to 4% virus-specific RNA, compared with 0.06 to 0.15% observed in uninfected cells. Sucrose gradient analysis of virus-specific RNA isolated from ASV-infected cells revealed two major classes of polyadenylated viral RNA with sedimentation values of 36S and 26-28S. Cells infected with transformation-defective ASV (virus containing a deletion of the sarcoma gene) contained 34S and 20-22S viral RNA species. Double-label experiments employing infected cells labeled initially for 48 h with [3H]uridine and then for either 30, 60, or 240 min with [32P]phosphate showed that the intracellular accumulation of genome-length RNA (36S) was significantly faster than that of the 26-28S viral RNA species.

Alpharetrovirus↗
PubMed1978

Matching with a key-peck response in concurrent negative reinforcement schedules.

In the absence of responding, pigeons were shocked under a variable-time schedule. Responses on either of two keys occasionally produced one minute of shock-free time. That is, pigeons' key pecks were reinforced with shock-free time under concurrent variable-interval schedules. The relative frequency of access to the one-minute shock-free periods was systematically manipulated. Pigeons tended to match both relative response rate and proportion of time spent on each key to the relative frequency of the shock-free periods. A best-fit linear regression equation accounted for over 95% of the variance in both relative response rate and time allocation. The data paralleled closely the results of concurrent schedules of positive reinforcement. These findings are consistent with a description of reinforcement as a transition to a higher-valued situation and suggest that common laws govern choice for both positive and negative reinforcement.

Journal Article↗
PubMed1977

Radioimmunoassay of creatine kinase-B isoenzyme in human sera: results in patients with acute myocardial infarction.

A radioimmunoassay was developed to measure serum levels of the B isoenzyme of creatine kinase(ATP: creatine N-phosphotransferase, EC 2.7.3.2) (CPK) in order to evaluate the time course and frequency of MB isoenzyme elevation in patients with acute myocardial infarction. The method can identify as little as 0.2 ng of the B portion of the CPK-MB isoenzyme, does not significantly crossreact with CPK-MM isoenzyme, and is not affected by storage of serum at --20 degrees CPK isoenzyme containing B subunits was detected in 48 out of 51 sera from normal adults; serum levels in these individuals ranged between 1.2 and 12.5 ng/ml [mean +/- SEM was 2.7 +/- 0.30 ng/ml]. The mean serum level of CPK-B isoenzyme in a pool of sera obtained from 100 normal subjects was 2.9 +/- 0.35 ng/ml; two patients with rhabdomyolysis that were studied had serum CPK-B isoenzyme levels of 2.5 and 3.5 ng/ml, respectively. In contrast, serum levels of the CPK-B isoenzyme were markedly elevated in sera from 18 patients with acute myocardial infarcts when obtained within 12 hr after hospital admission; the mean +/- SEM concentration was 56 +/- 7.8 ng/ml. We performed serial determinations on 14 patients with acute myocardial infarcts and demonstrated that maximal serum CPK-B levels occurred within the first 12 hr after admission and were lower thereafter. The serum concentration of B-containing CPK isoenzyme in 19 additional patients admitted with chest pain but without acute myocardial infarction was 3.4 +/- 0.50 ng/ml. Thus, radioimmunoassay measurement of CPK-B isoenzyme appears to be a useful and sensitive test for the detection of acute myocardial infarcts in patients.

Acute Disease↗
PubMed1977

Parameters affecting the maintenance of negatively reinforced key pecking.

Three negative reinforcement experiments employing a key-peck response are described. In Experiment I, pigeons shocked on the average of twice per minute (imposed condition) could produce, by pecking a key, an alternate condition with correlated stimuli. Delayed shocks were added, across sessions, to the alternate condition until pecking stopped. Two of three pigeons continued to peck despite a 100% increase in shock frequency. In Experiment II, pigeons were shocked in the imposed condition four times per minute. The postresponse delay to shock was held constant by delivering, in the alternate condition, the next shock, or the next two, three, or four shocks from the imposed-condition shock schedule. All three subjects continued to peck with no change in delay to the first two postresponse shocks but with a 75% reduction in shock frequency. In Experiment III, a response produced an immediate shock followed by a shock-free period. Three of four subjects continued to respond despite reduced delay to shock. Delay-to-shock or shock-frequency reduction was sufficient to maintain key pecking, but neither was necessary. The conditions that negatively reinforce the pigeon's key peck were similar to conditions that negatively reinforce the rat's bar press.

Journal Article↗
PubMed1976

The essential action of propranolol in hypertension.

The unique action of propranolol and other beta blockers in lowering raised arterial pressure is discussed. Although the onset of the antihypertensive effect is not immediate, many trials have confirmed the efficacy of these drugs. Animal experiments have thrown little light on the mechanism of action of beta blockers in hypertension: this may be because in animals, especially the rat, peripheral beta adrenoceptor vasodilatation is relatively more important than in man. Five principal theories have been advanced to explain the antihypertensive effect. None of these, the renin, central nervous system, cardiac, baroceptor or metabolite theory, is totally satisfactory. A new theory is proposed suggesting that the essential action is to diminish sympathetic nerve output by damping sensory input to the central nervous system from a heart whose capacity to respond to exercise and stress is blunted by beta adrenoceptor blockade.

Adrenergic beta-Antagonists↗
PubMed1976

The structure and formation of the byssus attachment plaque in Mytilus.

The byssus attachment plaque and the tissues responsible for its formation were studied in M. californianus by light microscopy and by transmission and scanning electron microscopy. It was shown that the plaque consists of at least three phases which ultrastructurally resemble three secretions considered to be collagen, mucoid material and polyphenol. The mucoid and polyphenol appear to mix as a colloidal suspension in which the latter is the continuous phase and forms the definitive bonding surface. Plaque collagen represents an extension of thread material into the cementing substance. Stimulated secretion within the ducts and distal depression of the mussel's foot shows a continuum of increasing heterogeneity from the inner toward the outer regions. This reflects the distribution of exocrine cell apices wherein exocytosis of polyphenol granules predominate deeply, mucous granules superficially and collagen granules in between. It is proposed that the morphology of the plaque conforms to theoretical physical-chemical requirements for adhesion under water.

Adhesiveness↗